JP3389097B2 - Powder coating composition for inner surface of cast iron pipe - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a powder coating composition for the inner surface of a cast iron pipe and an article coated with the composition. In particular, the present invention relates to a powder coating capable of coating a powder coating having excellent coating flexibility, impact resistance, corrosion resistance and barrier effect by an inexpensive and simple method, and the powder coating. Relates to a cast iron pipe obtained by using.

[0002]

2. Description of the Related Art In coating for the purpose of anticorrosion, various measures have been taken to prevent corrosion from a coating film defect which occurs when an object to be coated is subjected to physical impact. In the past, a method of avoiding the destruction of the anticorrosion layer by providing a sacrificial destructible layer such as mortar lining was used, but this causes an increase in the weight of the coated object, a decrease in transportability, and a sacrificial destructive layer. There was a problem that the destroyed part of the destroyed layer had to be repaired when buried. Further, a film forming method of a multi-layer film structure has been developed in which a polyolefin film formed by coating or forming an epoxy layer having a structure of two or more layers of an epoxy layer and a polyolefin layer and then winding the film into a thin roll is formed into a polyolefin layer. However, in all of these techniques, there is a problem that an interface exists between the epoxy layer and the polyolefin layer, and delamination occurs due to fine defects on the coating film surface. Further, in order to form a two-layer structure coating film with two coats and two bake, each apparatus for forming each layer is required, and the capital investment amount is inevitably increased. Furthermore, from the viewpoint of maintaining the water quality when the flow rate is very small, even if the seismic storage tank is in a static or flowing state, residual chlorine in tap water is not consumed and it is required to maintain the initial water quality for a long time. Has been done.

[0003]

SUMMARY OF THE INVENTION Therefore, the present invention provides a powder coating which can be applied by a simple and inexpensive method with a coating having excellent flexibility, impact resistance, corrosion resistance and barrier effect. An object is to provide a cast iron pipe obtained by coating the powder coating on the inner surface.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned object, and as a result, blended a polyolefin resin or a modified product thereof with an epoxy resin powder coating composition to obtain a powder. When it is made into a coating, the resulting powder coating composition forms a coating film having a two-layer structure by phase separation upon curing, and a coating film excellent in flexibility, impact resistance, corrosion resistance and barrier effect is obtained. Found to form. The present invention has been made based on such novel findings. That is, the present invention is characterized by blending 10 to 100 parts by weight of a polyolefin resin having a number average molecular weight of 3,000 to 20,000 or a modified product thereof with 100 parts by weight of an epoxy resin powder coating composition. The present invention relates to a powder coating composition for pipe inner surface.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The epoxy resin powder coating composition used in the present invention,
Contains epoxy resin, curing agent, pigment, additives, etc. Methods for synthesizing epoxy resins used in epoxy resin powder coating compositions are known to those skilled in the art. The epoxy resin is, for example, an epoxy equivalent of 600 to 2,000 g / e.
It is suitable that it is q, preferably 600 to 1,200 g / eq. Further, the epoxy resin having a softening point of 30 to 160 ° C., preferably 50 to 150 ° C., and particularly preferably 60 to 150 ° C. is suitable. When the softening point is less than 30 ° C, it is difficult to maintain the solid state at room temperature, which is not preferable for powder coating application. On the other hand, when the softening point is higher than 160 ° C., the reaction temperature becomes higher than the reaction temperature in the kneading machine in the melt kneading, and the coating film performance is seriously affected.

Specific examples of the epoxy resin include Epicoat series manufactured by Yuka Shell Epoxy Co., Ltd., for example, Epicoat 1004 and Epiclon 3050 manufactured by Dainippon Ink and Chemicals, Inc. The phase transition temperature of the epoxy resin is, for example, 20 ° C. or higher, preferably 30.
C. or higher, particularly preferably 40.degree. C. or higher. When the phase transition temperature is lower than 20 ° C, the powder properties such as blocking are likely to deteriorate when stored at room temperature, which is not preferable. The epoxy resin is suitably added in an amount of, for example, 20 to 100% by weight, preferably 30 to 80% by weight, based on the weight of the epoxy resin powder coating composition.

The curing agent is not particularly limited as long as it is used in the epoxy resin powder coating composition, and various curing agents can be used. As such a curing agent, for example, a curing agent used in a nucleophilic substitution reaction in which a glycidyl group is opened can be used. For example, as the curing agent, amine, amidine, acid anhydride, carboxylic acid-containing polymer (for example, polyester,
Acrylic, etc.), phenol having a novolac structure, phenol having a bisphenol epoxy as a skeleton, DDM
(Diaminodiphenylmethane), DBU (diazabicycloundecene), DDA (decanedicarboxylic acid), AD
Examples thereof include H (adipic acid dihydrazide) and imidazole adducts. The curing agent is suitably used in an amount of, for example, 1 to 20% by weight, preferably 2 to 10% by weight, based on the weight of the epoxy resin powder coating composition.

As the pigment, pigments usually used in paints can be used. For example, as the color pigment, titanium oxide, red iron oxide, iron oxide, quinacridone, carbon black, azo compounds, dioxane, threne, phthalocyanine metal complexes, and other substances mainly containing metal salts can be listed.
Examples of extender pigments include barium sulfate, silicon dioxide, talc, calcium carbonate, potassium titanate whiskers, aluminum borate whiskers, wollastonite,
Aluminum oxide, asbestos, ceramic powder, etc. can be listed. The pigment is suitably used in an amount of, for example, 0 to 80% by weight, preferably 10 to 60% by weight, based on the weight of the epoxy resin powder coating composition. As additives, leveling agents, waxes, defoamers, flame retardants, antioxidants, UV absorbers and the like can be commonly used.

The additives are suitably used in an amount of, for example, 0.1 to 10% by weight, preferably 0.3 to 7% by weight, based on the weight of the epoxy resin powder coating composition. .
In the present invention, various resins can be used as the olefin resin blended in the above-mentioned epoxy resin powder coating composition as long as they are polymerized with olefin as a monomer. Examples of the olefin include olefins having 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, such as ethylene, propylene and butylene. The polyolefin resin may be a homopolymer or a copolymer. Further, in the present invention, a modified product of polyolefin can be used. As a modified polyolefin, for example, a monomer capable of copolymerizing with an olefin, for example, a vinyl-polymerizable monomer (for example, styrene, an acrylic monomer, a methacrylic monomer, a maleic acid monomer, etc.) is used for modification. You can In particular, by using a (meth) acrylic acid monomer in combination, it is possible to improve the adhesiveness or miscibility with the base material or the epoxy resin by introducing a carboxyl group or a carbochelate group into the polyolefin resin.

The polyolefin resin or its modified product has, for example, a number average molecular weight of 3,000 to 20,000, preferably 8,000 to 18,000, and particularly preferably,
Those having 8,000 to 15,000 are suitable.
If the number average molecular weight is less than 8,000 , a mechanical share during kneading causes a pseudo compatible state with the epoxy resin, phase separation during curing hardly occurs, and a two-layer structure coating film is formed. It becomes difficult, which is not preferable. On the other hand, if the number average amount exceeds 20,000, an excessive temperature rise of the composition at the time of kneading is caused, which adversely affects the properties of the coating film, which is not preferable. The polyolefin resin is 10 to 100 parts by weight, preferably 15 to 80 parts by weight, particularly preferably 20 to 6 parts by weight, based on 100 parts by weight of the epoxy resin powder coating composition.
It is suitable to blend in an amount of 0 parts by weight. When the amount of the polyolefin resin is less than 10 parts by weight, the amount of the polyolefin phase-separated from the epoxy resin component is small at the time of forming the coating film, and the polyolefin is scattered on the surface of the epoxy coating film. Unable to take a coating of structure. Further, when it is 100 parts by weight or more, it becomes difficult to pulverize the pellets formed after kneading in the room temperature region, and it is necessary to use freeze pulverization and the like, which easily causes an increase in cost required for pulverization. Absent.

In the present invention, the above epoxy resin powder coating composition contains a polyolefin resin or a modified product thereof in order to further improve the characteristics of the powder coating. For example, a petroleum resin or a modifier may be used as a modifying agent. Urea aldehyde resin, terpene and the like can be appropriately added. The epoxy resin powder coating composition and the polyolefin resin or modified products thereof are uniaxial or biaxial after mixing these raw materials at room temperature.
The kneading is performed using a kneading machine such as a shaft extruder that is commonly used for producing powder coatings. The pellets formed by kneading are pulverized using a pulverizer such as a pin mill and adjusted to an arbitrary particle size distribution using a sieve or the like. The average particle diameter of the powder coating material containing the polyolefin resin or its modified product is, for example, 20 to 20.
It is suitable that the thickness is 150 μm, preferably 30 to 130 μm.

The powder coating thus obtained is coated by an electrostatic coating machine, a triboelectrification coating machine, fluidized dipping, in-molding, etc. and baked in a hot air oven, infrared oven, induction heating oven, etc. Can be formed.

[0013]

The present invention will be described in more detail below with reference to examples. In the examples, “parts” and “%” are based on weight. The components used in the following examples or comparative examples are as follows. Epoxy resin Epicoat 1004 (Epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd.) Properties: Epoxy equivalent 915 g / eq, softening point 97 ° C, phase transition temperature 48 ° C Polyolefin resin or its modified product 1. Polyolefin resin HI-WAX800P (high-density polyethylene (HDPE) manufactured by Mitsui Petrochemical Co., Ltd.) Characteristics: number average molecular weight 8000 2. Modified product of polyolefin resin MODIC KM-05 (Modified product of linear low-density (LLDPE) polyethylene base maleic anhydride manufactured by Mitsubishi Chemical Co., Ltd.) (Preparation of powder coating A) The following components are kneaded, pulverized, and classified. Powder coatings A and B having an average particle diameter of 100 μm were prepared. Parts by weight (A) parts by weight (B) Epicoat 1004 (made by Yuka Shell Epoxy Co., Ltd.) 65 parts 65 parts adipic acid dihydrazide (ADH) (hardening agent) 4 parts 4 parts barium sulfate (extrinsic pigment) 25 parts 25 parts titanium dioxide (Coloring pigment) 5 parts 5 parts Carbon black (coloring pigment) 1 part 1 part Polyolefin resin modified product 80 parts 12 parts

(Preparation of powder coating C) A polyolefin resin is used in place of the modified polyolefin resin, the addition amount is 40 parts by weight, and the powder coating C having an average particle diameter of 81 μm is used.
It was created. (Preparation of Powder Coating D) A powder coating D having an average particle size of 100 μm was prepared in the same manner as the powder coating A except that the polyolefin resin or its modified product was not used. (Preparation of powder coating E) A powder coating E having an average particle size of 100 μm was prepared in the same manner as the powder coating A except that 5 parts of the modified polyolefin resin was used. (Preparation of powder coating F) Polyolefin resin modified product 150
A powder coating material F having an average particle size of 100 μm was prepared in the same manner as the powder coating material A, except that a part thereof was used.

<Examples 1 and 2 and Comparative Examples 1 to 4> The obtained powder coating materials A to F were electrostatic powder coating machines (Matsuo Sangyo PG
-1 type) was applied to a cold-rolled steel sheet having a thickness of 1.2 mm at a voltage of −60 kV so as to have a thickness of 300 μm to 400 μm, and baked at 200 ° C. for 20 minutes. Further, in order to create a conventional two-layer structure coating film, after coating and baking the powder coating material C, fluid immersion grade polyethylene (Flowsen: product name of Sumitomo Seika) is overcoated and the following various tests are conducted. It was The results are shown in Table 1 below. (Test item) <Coating state> The state of the coated surface is visually determined. ◯: Good x: Poor <State of vertical cross section of coating film> After cutting the coated plate and polishing the end faces, the phase separation state of the vertical cross section of the coating film was observed using a polarizing microscope. ◯: Separated two-layer structure coating film is formed. X: A coating film having a two-layer structure is not formed. <Bending resistance> JIS K5400 8.1 compliant: Pass: X: Fail <Impact resistance> JIS K5400 83.2 compliant The weight drop height that does not cause cracking and peeling of the coating film is displayed. <Residual chlorine consumption> Two glass plates coated on both sides with an area of 70 mm x 100 mm were immersed in 1 L of sample water adjusted to an initial chlorine amount of 1.2 mg / L, and the environment was 20 ° C and 60% humidity. The sample was left to stand and the residual chlorine amount after 1 week was measured by the o-tolidine method, and the consumption amount from the initial value was calculated.

[0016]

[Table 1] Table 1 Examples Comparative Example 1 2 3 1 2 3 4 Used ABCDFEDF + powder coating Polyethylene coating film characteristic coating film state ○ ○ ○ ○ ○ × ○ ○ vertical section of coating film ○ ○ ○ × × ○ ○ Condition Bending resistance ○ ○ ○ × × ○ ○ Impact resistance (cm) 50 50 50 50 50 50 0 50 Adhesion 100/100/100/100/100/80/70/100 100 100 100 100 100 100 Residual chlorine 0.45 0.5 0.4 0.9 0.7 0.4 0.4 Consumption (mg / L) From the above table, when the epoxy resin powder coating composition is blended with the polyolefin resin or its modified product in a predetermined amount,
A coating film having excellent flexibility, impact resistance, corrosion resistance and barrier effect can be obtained (Examples 1 to 3). Moreover, since it only needs to be painted once, compared to the case of forming a conventional two-layer structure coating film,
It is simple and the cost can be reduced accordingly.
On the other hand, Comparative Example 1 containing no polyolefin resin or its modification and the content of the polyolefin resin were 1
In Comparative Example 2 with less than 0 parts by weight, a pseudo two-layer structure coating film was not formed in the vertical section of the coating film, and the bending resistance was also unacceptable. Further, in Comparative Example 3 in which the content of the polyolefin resin or its modified product exceeds 100 parts by weight, the state of the coating film was poor, and the impact resistance and adhesion were poor. Furthermore, in Comparative Example 4 in which the conventional two-layer structure coating film was formed, the adhesion was poor.

[0017]

The coating film formed from the powder coating composition of the present invention comprises two layers, an epoxy layer and a polyolefin resin layer, which are excellent in flexibility, impact resistance, corrosion resistance and barrier effect of the coating film. The structure can be realized by the coating film forming process of one coat and one bake, and the amount of capital investment can be reduced.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takaaki Deguchi 1-12-19 Kitahori, Nishi-ku, Osaka City, Osaka Prefecture Kurimoto Iron Works Co., Ltd. (72) Inventor Kazuhito Hanano 1-Kitahorie, Nishi-ku, Osaka-shi, Osaka 12-19 Incorporated company Kurimoto Ironworks (72) Inventor Sho Sho Masuda 58-102 Hatanaka, Honmachi, Iwakura City, Aichi Prefecture (72) Inventor Toshikazu Ikeda 5-45, Aikigaoka, Kani City, Gifu Prefecture (72) Tetsuo Nagao Aichi Prefecture 1-5-8 Takazadai, Kasugai City (72) Inventor Susumu Nakai 309-7 Handa, Kaizuka City, Osaka Prefecture (56) References JP-A-61-148274 (JP, A) JP-A-10-95929 (JP, A) ) JP-A-8-290509 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09D 123/00 C09D 5/03 C09D 163/00

Claims (2)

(57) [Claims] 1. A tap water comprising 100 parts by weight of an epoxy resin powder coating composition and 10 to 100 parts by weight of a polyolefin resin having a number average molecular weight of 8,000 to 20,000 or a modified product thereof . The resin powder coating composition for the inner surface of the cast iron pipe. 2. A water supply, characterized in that painted cast iron pipe inner surface resin powder coating composition for tap water according to claim 1
Cast iron pipe for water .